The related art assumes Gaussian distribution with respect to an interference signal in order to perform decoding at low complexity. Therefore, to make a characteristic of an interference signal close to Gaussian maximally, a modulation scheme of a Quadrature Amplitude Modulation (QAM) basis is primarily used. However, it is generally known that a channel capacity of a non-Gaussian channel is greater than that of a Gaussian channel. Therefore, when decoding is properly performed, a higher decoding performance may be obtained in a non-Gaussian channel rather than a Gaussian channel.
Accordingly, development of a modulation scheme allowing an interference signal to conform to the non-Gaussian distribution has been needed, and a modulation scheme proposed as a result of the development is Frequency and Quadrature-Amplitude Modulation (FQAM). The FQAM is a hybrid modulation scheme where the QAM and Frequency Shift Keying (FSK) are combined, and FQAM has both the advantage of a high spectral efficiency of the QAM and the advantage of making an interference signal of the FSK non-Gaussian.
The FQAM has a characteristic of being not suitable for a bit-to-symbol scheme. Therefore, in case of applying the FQAM, a Bit-Interleaved Coded Modulation (BICM) channel capacity is lower than a Coded Modulation (CM) channel capacity. Since, in general, the CM channel capacity increases even more as an alphabet size of a channel code is large, in order to obtain high performance using the FQAM, it is preferable to combine the FQAM with a non-binary channel code where the alphabet size is large. The alphabet size indicates a number of candidates of an encoding output value. At this point, complexity of a non-binary channel code increases exponentially as the alphabet size increases. Therefore, consequently, to use the advantage of the FQAM, channel encoding and decoding processes, whose complex is very high, are needed.
For improvement of a decoding performance, an FQAM technique may be considered, but for an efficient use of the FQAM, channel encoding and decoding processes, whose complexity is high, are needed. Therefore, an alternative for reducing complexity of encoding and decoding while maintaining the advantage of the FQAM needs to be proposed.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.